1. Field of the Invention
The present invention relates to a method for generating luminescence in one or more buried layers in a multilayer compound semiconductor material. More specifically, the present invention uses an electrically conducting fluid to contact a multilayer compound semiconductor material. Some examples of inorganic compound semiconductor materials of interest include AlGaAs, InGaAs, GaInP InGaN and CdZnSe. Examples of organic compound semiconductor materials of interest include Gaq3 (q=8-hydroxyquinolate), Alq2OPh and PPV (poly-paraphenylenevinylene). When an electrical current is passed into the multilayer semiconductor material, electrons and holes are generated in the material which recombine in one or more buried layers to produce light. The characteristics of the light emitted through the surface of the material and through the transparent conducting fluid in contact with the surface can be measured and used to determine the quality of the multilayer compound semiconductor material or wafer. Using various processing techniques to create individually addressable areas on the surface of the wafer converts the conducting fluid/patterned-wafer combination into a device capable of information display.
2. Background of the Invention
Group III-V inorganic multilayer compound semiconductor materials have found wide use in high speed electronic and various optoelectronic applications. Group II-VI inorganic semiconductors have recently assumed importance because new, short wavelength lasers have been produced using ZnSe-based materials. In the last few years, organic semiconductor materials such as Gaq3 and PPV have received considerable attention for possible use in low cost flat panel displays. An inexpensive and simple method for determining the quality of such semiconductor materials would decrease fabrication costs and broaden their use. Laser induced luminescence has been used to determine the quality of both single and multilayer wafers fabricated from such materials. However, when the multilayer wafer contains a p-n junction, it is very difficult to determine material quality since the relationship between pump laser intensity and effective current density is difficult to establish. This is due to the fact that the effective current density provided by the laser beam depends on the reflectivity, absorption and transmission characteristics of the wafer at the lasing wavelength and the nature of the minority carrier transport processes in the wafer. Using a transparent, electrically conducting fluid to generate luminescence, one can easily measure the actual current density through the wafer and thence obtain an accurate determination of material quality.
In the area of information display, light-emitting diode arrays are well-known although they have not been widely used because of high fabrication costs. An inexpensive method for driving such arrays using a transparent, electrically conducting fluid would broaden the use of such devices. In addition, the encapsulation process required to achieve useful life-times for multilayer organic semiconductor light-emitting devices may be simplified through the use of electrically conducting drive fluids thereby broadening their use.